Personal computer systems in general and IBM.RTM. personal computers in particular have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard (or system planar) to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses.
Beginning with the earliest personal computer, such as the IBM Personal Computer, it was recognized that software compatibility would be of utmost importance. In order to achieve this goal, an insulation layer of system resident code, also known as "firmware", was established between the hardware and software. This firmware provided an operational interface between a user's application program/operating system and the hardware device to relieve the user of the concern about the characteristics of hardware devices. Eventually, the code developed into a BASIC input/output system (BIOS), for allowing new devices to be added to the system, while insulating the application program from the peculiarities of the hardware. The importance of BIOS was immediately evident because it freed a device driver from depending on specific device hardware characteristics while providing the device driver with an intermediate interface to the device. Since BIOS was an integral part of the system and controlled the movement of data in and out of the system processor, it was resident on the system planar and was shipped to the user in a read only memory (ROM). For example, BIOS in the original IBM Personal Computer occupied 8K of ROM resident on the planar board. Newer versions of BIOS are stored both in ROM and in EEPROM or in the hard drive.
A problem encountered by many personal computer users is the inadvertent introduction of so-called computer viruses into the computer system. Computer viruses are programs that generally are able to make copies of themselves and are capable of affecting the operation of the subject computer system. These computer viruses can cause unrecoverable errors and can have large economic impact. There are several virus detection programs available to scan for a virus on the computer.
Normally, a computer's power-on self test (POST) would run to completion, then read in the Master Boot Record (MBR) off the booting device (usually a disk), and pass control to that device. The MBR loads the operating system boot record which then loads the rest of the operating system. A computer virus author may design the virus so that it gets into the MBR or the operating system boot record. This creates the opportunity for a virus to acquire control of the system before the operating system has a chance to load and run any virus detection program.